maikop formation

google doesn't help. geologically speaking, what is a "maikop formation"?

Apparently, a distinctive Oligocene–Miocene sedimentary stratification of rock first identified in the vicinity of Maikop in the Republic of Adygea in the North Caucasus, but extending into Azerbaijan and Turkmenistan.

If you need a more technical definition than that you'll have to consult a geologist.

. . . or VinnyD and Google:

The Oligocene–Miocene Maikop Series is a world-class source rock responsible for much of the oil and gas found in the South Caspian Basin. It is composed of up to 3 km of marine mudstone, and contains a nearly continuous record of deposition during progressive tectonic closure of the basin as the Arabian Peninsula converged northward into Eurasia.

More.

Ah, echoes of my youth! This post reminds me that one of my college textbooks was "Stratigraphy and Sedimentation."